Third part of porting Chrome Ash to Windows 7

ash/host/window_tree_host_factory.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef ASH_HOST_WINDOW_TREE_HOST_FACTORY_H_
 #define ASH_HOST_WINDOW_TREE_HOST_FACTORY_H_
 
 #include "ash/ash_export.h"
 #include "ui/gfx/rect.h"
 
 namespace aura {
 class WindowTreeHost;
 }
 
 namespace ash {
 
 class ASH_EXPORT WindowTreeHostFactory {
  public:
   virtual ~WindowTreeHostFactory() {}
 
   static WindowTreeHostFactory* Create();
+  static WindowTreeHostFactory* CreateForTest();
 
   // Creates a new aura::WindowTreeHost. The caller owns the returned value.
   virtual aura::WindowTreeHost* CreateWindowTreeHost(
       const gfx::Rect& initial_bounds) = 0;
 
  protected:
   WindowTreeHostFactory() {}
 };
 
 }  // namespace ash
 
 #endif  // ASH_HOST_WINDOW_TREE_HOST_FACTORY_H_